The present invention relates to an improved car-used electric fuel pump.
A conventional car-used electric fuel pump is shown in FIG. 1, wherein a fuel inlet member 11 is disposed at one end of a hollow housing 10. Referring to FIG. 2, a fuel inlet board 12, a middle ring member 13 and a fuel outlet board 16 are disposed on an inner side of the fuel inlet member 11 in sequence. The fuel inlet board 12 is formed with an arch fuel inlet 121 and an opposite pressure-balancing groove 122. An outer rotor 14 having inner teeth and an inner rotor 15 having outer teeth are engaged with each other and disposed in an eccentric hole of the middle ring member 13. The inner rotor 15 is formed with a central cross hole 151. An arch fuel outlet 161 is formed on the fuel outlet board 16 in alignment with the pressure-balancing groove 122 of the fuel inlet board 12. A DC motor 17 is disposed behind the fuel outlet board 16. A positive and a negative terminals of the motor are respectively connected with a positive and a negative electrodes 19 which are integrally molded together with a fuel outlet member 18. The motor 17 has a shaft 171 a front of which is cross-shaped for inserting into the central cross hole 151 of the inner rotor 15 for driving the same.
Please refer to FIG. 3. When the DC motor 17 drives both the inner rotor 15 and the outer rotor 14 to synchronously rotate, the space between the inner and outer rotors near the fuel inlet 121 is gradually increased and the fuel is sucked inward, while the space between the inner and outer rotors near the fuel outlet 161 is gradually reduced so that the sucked inward fuel is further discharged from the fuel outlet 161 to flow through the DC motor 17 outside the fuel outlet member 18.
In the above arrangement, because the outer rotor 14 is driven by the inner rotor 15 to eccentrically rotate relative to the middle ring member 13, the middle ring member 13 must be assembled with the fuel outlet board 16 with quite accurate alignment. Otherwise, in case of a slight error, the outer rotor 14 is likely to fail to rotate. Moreover, the motor shaft 171 is connected with the inner rotor 15 by means of accurately inserting the front end of the shaft 171 into the central cross hole 151 of the inner rotor 15. In case the central axial line of the assembly of the middle ring member 13, outer rotor 14 and inner rotor 15 is deflected from the central axial line of the motor, the operation will be unsmooth.
Therefore, it is necessary to provide an improved car-used electric fuel pump to eliminate the above shortcomings existing in the prior art.